Epicentre of Mass Coral Bleaching – Still So Beautiful (Part 1)

It is all over the news, and the news across the world, the Great Barrier Reef is bleaching – again.   Children can’t sleep at night: it is not only the war in the Ukraine, but also our apparent disregard for nature that is keeping them awake.

Except!

I went to the very epicentre of the claimed latest severe mass coral bleaching on 10th April 2022, and I found a coral wonderland.

There was some bleaching, especially around the perimeter of John Brewer Reef – on the sandy sea floor where the Australian Institute of Marine Science (AIMS) surveys and concludes coral cover is never more than 30% – but most of John Brewer Reef is still covered in more than 80% colourful corals.    This high percentage is denied by AIMS because they never survey the reef crest.

At John Brewer Reef just yesterday, I swam over the top – over the reef crest – and I also swam along the walls that drop down to the sandy sea floor.

My buddy swam in front of me between the walls of coral at John Brewer Reef on 10th April 2022. Photographed by Jennifer Marohasy.

I will show you some of the snap shots that I took with my Olympus TG6, no lights.  I also swam around the sandy perimeter, and I will show you these photographs in my next blog post – that will be Part 2 of this series.   In Part 3 and 4 I plan to show you video of transects that will be swam later in the week when I return to John Brewer Reef with one of Australia’s best underwater cinematographers.

My buddy swimming along the front wall of John Brewer Reef on 10th April 2022. Photographed by Jennifer Marohasy.

John Brewer Reef is 70 kms (38 nautical miles) east of Townsville, part of the central region of the Great Barrier Reef.   Rising from the sandy sea floor are two huge flat-topped blocks of consolidated limestone that represent layer upon layer of dead coral (that you can’t see) with a topping (that you can see) of colourful plates and so many tiny fish.  Running between these two reefs is a deep canyon with walls of more coral and more fish.

Most of the corals were very healthy with lots of chocolate brown zooxanthellae, but you can see a bleached coral in the distance that is very white.  Photographed by Jennifer Marohasy at John Brewer Reef on 10th April 2022.

While most of the corals at the reef crest were healthy, there were some corals that were bleaching white and others were bleaching colourful.

The pink to purple coloration in some of the corals at the reef crest is not from zooxanthellae, which are the symbiotic algae, but rather from increased pigment accumulation from the coral itself as the zooxanthellae are expelled.  Zooxanthellae are expelled when the coral becomes stressed from water that is a bit too hot or a bit too cold.  These colourful corals are often described as fluorescing.

This plate coral has bleached and is fluorescing. Photographed by Jennifer Marohasy at John Brewer Reef on 10th April 2022.
This is a closeup of a plate coral with its pink tips are still alive.  The coral colony will likely recover.  According to the technical literature, some corals florescence/go this pink colour within 2 to 3 weeks of exposure to unusually warm temperatures.  More usually this coral would be a deep chocolate brown. Photographed by Jennifer Marohasy at John Brewer Reef on 10th April 2022.
This is a close-up of a brown plate coral, that has not bleached and is not fluorescing. Photographed by Jennifer Marohasy at John Brewer Reef on 10th April 2022.
This is a closeup showing the coral polyps of a healthy brown coral colony (top) and also a bleached colony (foreground). If you look closely you will see tentacles that enable the coral to feed even when all the zooxanthellae have been expelled. Photographed by Jennifer Marohasy at John Brewer Reef on 10th April 2022.

***

The photograph at the very top of this blog post was taken just yesterday (10th April 2022) while I (Jennifer Marohasy) swam over the top of John Brewer Reef.  The coral in the foreground is not bleached, but rather naturally beige-coloured and with naturally white tips.  The very pink coral in the centre of the photograph is bleaching colourful. The pink to purple coloration in some of the corals at the reef crest is not from zooxanthellae, which are symbiotic algae, but rather from increased pigment accumulation from the host tissue/the coral itself as the zooxanthellae are expelled.

via Jennifer Marohasy

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April 11, 2022 at 01:14AM

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